I am restoring a burnt JD 855 tractor and all that is left is to get power steering to work. Initially a seal in the Parker HGF steering valve was leaking so I took pump apart and completely rebuilt. When I reinstalled it, the pump would initially work when air was in steering ram, but then would lock in both directions afterwards. I took the pump apart thinking I got the valve plate or springs positioned wrong, etc. but it didn"t fix it. I then bought a used pump from a tractor being junked but that didn"t fix the problem either.
When I unscrew lines at the steering ram, fluid comes out each side as it should. However, when they are attached to the ram they won"t force fluid out of the other side of the ram and it locks. I thought maybe it was the cold weather and fluid was to thick. However, even when the front is jack up, it won"t work. The rest of the tractor hydraulics (3pt., transmission, etc.) all work good in the cold temps so I don"t think it is cold oil.
I have also tried to couple the two lines to the ram together to isolate the problem and rule out the ram. The steering valve still locks up. Thinking it was a blocked return line I took that off the valve and let it go in a pail. Good flow, about 1 gal. in less than 30 sec. and no sign of any pressure blockage but pump still locks up right away. I uncoupled the lines going to the ram and put those in pail and then the steering valve works as it should spitting oil from the right hose as the steering wheel is turned left or right. The pump doesn't lock then.
Anybody have any ideas? I am really at wits end! I have a repair diagram of the Parker steering valve if needed. Thanks!
When I unscrew lines at the steering ram, fluid comes out each side as it should. However, when they are attached to the ram they won"t force fluid out of the other side of the ram and it locks. I thought maybe it was the cold weather and fluid was to thick. However, even when the front is jack up, it won"t work. The rest of the tractor hydraulics (3pt., transmission, etc.) all work good in the cold temps so I don"t think it is cold oil.
I have also tried to couple the two lines to the ram together to isolate the problem and rule out the ram. The steering valve still locks up. Thinking it was a blocked return line I took that off the valve and let it go in a pail. Good flow, about 1 gal. in less than 30 sec. and no sign of any pressure blockage but pump still locks up right away. I uncoupled the lines going to the ram and put those in pail and then the steering valve works as it should spitting oil from the right hose as the steering wheel is turned left or right. The pump doesn't lock then.
Anybody have any ideas? I am really at wits end! I have a repair diagram of the Parker steering valve if needed. Thanks!